Review

The Rokinon 135mm F/2 was Built for Astrophotography

In this post, I’ll explain why I think the Rokinon 135mm F/2 is the perfect addition to an arsenal of astrophotography lenses.

Deep sky astrophotography is often associated with a camera and telescope, but the truth is there are a lot of great camera lenses for astrophotography out there. In the past I’ve covered a number of different lenses, from the Rokinon 14mm F/2.8 to the Canon EF 300mm F/4L.

As you know, camera lenses come in varying focal lengths, apertures, and optical quality. Astrophotography is one of the ultimate tests of lens quality, as long exposure photography of deep sky objects in space can highlight issues that are hidden during daytime photography.

In this post, I’ll share my results using an affordable prime telephoto lens for astrophotography, the Rokinon 135mm F/2.0 ED UMC. The version I have has the mount for Canon EOS camera bodies, but there are several different lens mounts available on Amazon.

This lens is available for several camera mounts, including Nikon, Sony, Pentax, Samsung, and Fuji. I purchased this lens for the purposes of wide-field deep sky astrophotography from my light polluted backyard (shown below), and when traveling to a dark sky site.

Taking images at this focal length from the city will swell issues with gradients, especially when shooting towards the “light dome”. For this reason, a combination of a good light pollution filter, and the use of flat calibration frames is recommended. Before I go any further, I’d like to share a photo from Gabriel Millou of the Andromeda Galaxy using a Canon 1300D.

The Andromeda Galaxy using the Rokinon 135mm F/2.0 ED UMC lens.

To see even more example photos using the Rokinon 135mm lens (or Samyang branded version), go ahead a perform a search on Astrobin or Flickr, with the appropriate filter. I think you’ll find that this lens is behind some of the most amazing wide field astrophotography images online!

The Rokinon 135mm F/2 ED UMC

The full name of this lens is the Rokinon 135mm F/2 ED UMC, with “ED” standing for extra-low dispersion, and UMC referring to the “ultra multi-coated” optics. This is a fully manual lens, meaning that it does not have autofocus, and you must manually select the f-stop using the aperture ring at the base of the lens.

Manually focusing a lens for astrophotography is nothing new, but the manual aperture ring adjustments may feel a little strange at first.

Rokinon lenses are made in Korea, and so is the Samyang variation. The full extent of the relationship between Rokinon and Samyang is unknown to me, but the packaging on my lens says “Technology by Samyang Optics”. I typically shoot with Canon lenses, but the potential for low light photography (whether that’s astrophotography or the ability to film at dusk) caught my interest.

The diameter of the lens is 77mm, with a non-rotating filter mount on the objective lens. The lens hood is removable (and reversible), which makes packing the Rokinon 135mm away into the included lens pouch possible. The presentation, and hands-on look and feel of the 135mm F/2 lens is impressive considering the reasonable price of this lens.

The aperture range of this of this lens is F/2 to F/22, with 9 diaphragm blades (aperture blades) that work in harmony to set your f-stop. The aperture ring is marked with each f-stop, and you need to manually click through F/2 – F/22 and watch the blades do their work. It’s actually kind of neat to watch!

I ordered this lens on Amazon, utilizing my Amazon Prime membership. The lens arrived next day, less than 24 hours after I hit the order button. The lens came in a handsome box, with core specifications and a lens construction diagram printed on the side. The Rokinon 135mm F/2.0 includes a lens hood, lens pouch, front and rear lens caps, and a 1 year Rokinon manufacturer warranty.

First Impressions

Overall, the lens feels very solid and well constructed. The finish and texture of the Rokinon 135mm F/2 is a step up from the 14mm F/2.8 I ordered a few years ago.

The spec sheet for the Rokinon 135mm F/2 boasts a number of qualities, with the ones listed below being the most important when it comes to night photography and astro. Based on my handful of experiences with this lens in the backyard, I have found these traits to hold true.

Low-Light Performance

Low Chromatic Abberation

Low Flare and Ghosting

The image below shows a region of Sagittarius including many deep sky objects in the field. The photo itself is nothing special, as my light polluted backyard skies require several hours worth of integration to produce a pleasing image. However, it is a great point of reference for the field of view you can expect with this lens.

A portion of Sagittarius including the Lagoon Nebula and Trifid Nebula. 42 x 90-seconds at ISO 400.

The Rokinon website lists this lens as being useful for portraiture photography, and most telephoto applications. The shallow depth of field present at it’s maximum aperture does indeed create a pleasing bokeh.

The lens hood is not petal shaped, which is great news for those using this lens for astrophotography. The flat lens hood design allows you to easily take flat frames with the Rokinon 135mm using the white t-shirt method, or using a flat panel.

I should mention that I have only tested this full frame lens using my astrophotography DSLR’s, all of which are crop-sensor camera bodies. This creates an effective focal length of roughly 200mm, a useful magnification for a wide variety of astro-imaging scenarios.

I am no stranger to the full manual control of this lens, for both aperture and focus. The Rokinon 14mm F/2.8 was the first lens I had ever used like this, and these aspects do not hinder the astrophotography experience whatsoever.

A Full Frame, Prime Lens

The Rokinon 135mm F2.0 is considered to be a full frame lens, because it can accommodate a full frame image sensor with its 18.8 degree angle of view. In this review, however, I am using the lens on a corp sensor (APS-C) Canon EOS 60Da, which puts the field of view at 12.4 degrees.

“Prime” means that this lens is fixed at 135mm, it is not a zoom lens that allows for focal length adjustments. Prime lenses are typically lighter as they do not need the additional glass and mechanics required to zoom at varying magnifications.

Generally, prime lenses have a reputation for being slightly sharper, and I have found that to be true whether I am shooting a nebula, or a Scarlet Tanager.

The optical design includes one extra-low dispersion (ED) lens element to control chromatic aberration, and “ultra multi-coatings” (UMC) to both improve light transmission and reduce flare.

The flat lens hood is great for taking flat frames after a night of astrophotography.

Low Light Capabilities at F/2.0

The F/2.0 maximum aperture of the Rokinon 135mm lens offers a chance to collect a serious amount of signal in a single shot. This allows for less aggressive camera settings for night photography such as using a lower ISO setting, and even a shorter exposure.

Of course, when it comes to astrophotography, this can create some challenges as well. Focusing a “wide open” F/2 lens is demanding of the optics, especially on a field of stars in the night sky.

One way to combat potential soft images and chasing perfect focus all night is to stop the lens down to F/2.8 or even F/4. Your images have a chance at remaining sharper once critical focus has been achieved, but now you have lost the extra light gathering power you wanted. It’s a trade off, and one that seems to surface time and time again in this hobby.

Although typically unused in astrophotography, I did get a chance to see the beautiful bokeh this lens creates when shooting at F/2. The aesthetic quality of the blur in the out-of-focus parts of the image are buttery smooth and soft.

What I Really Like

Although this lens feels solid, it is rather light when compared to a telescope. When coupled with my Canon DSLR camera, the entire system weighs just over 3 pounds. That means that doesn’t require a robust equatorial telescope mount as a larger, heavier telephoto lens would.

A camera tracker (or “star tracker”) is necessary for long exposure deep sky astrophotography, but a compact model such as the iOptron SkyTracker or Sky-Watcher Star Adventurerwill do just fine.

This lens has a long focus adjustment ring, with great tension. The focuser adjustment rotates roughly 270 degrees, meaning fine tuning on a bright star is more precise. You’ll never have to worry about losing your position just by touching the lens, but you can always tape the position down to be sure.

The Rokinon 135mm F/2.0 ED UMC is one of the most affordable and practical lenses for astrophotography on the market. Sure, the “Nifty 50” is an incredible value (and a LOT cheaper), but the 135mm puts you within range of some of the best astrophotography targets in the night sky.

I’ve spent a handful of nights testing this lens in my Bortle Scale Class 6/7 backyard, and my results live up to the hype it gets in terms of astrophotography performance.

Comparable Lenses (Chart)

Lens Comparison

Over the years, I’ve shot deep sky targets at varying focal lengths from 50mm to over a 1000mm. The closest I’ve been to the 135mm range is 105mm on my Canon 24-105 zoom.

Not only does the Rokinon 135 add additional reach, but I can also now shoot at F/2, instead of F/4 on the Canon. Below, are a few examples of astrophotography images I’ve taken with lenses of varying focal lengths.

As you can see, the magnification of the lens used will dictate the type of projects you shoot.

The RedCat is deeper at 250mm, and after that you’re into 300-400mm territory which pulls galaxies and nebulae even closer. Why take a step back from 250 to sit between the RedCat and the 24-105?

It’s all about framing.

Image Scale at 135mm

From the moment I reviewed the first sub-exposure on the display screen of my camera, I feel in love with the mid-range magnification of a 135mm lens. My first shot was a section of the constellation Sagittarius that included the Lagoon Nebula, and Trifid Nebula.

If you want to preview the image field you can expect with a particular camera sensor and lens combination, Stellarium features a useful tool. The Image Sensor Frame tool lets you enter in the size of your camera sensor, and focal length of your lens (or telescope) to display a frame over the star map.

This is a very practical way to plan your next astrophotography project, and especially handy when using a wide field lens like the Rokinon 135mm F/2.

You can use Stellarium to preview the image scale with the 135mm lens and your DSLR.

At 135mm, you can get really creative about the object or objects you shoot and where you position them within the frame.

And because you can shoot between F/2 and F/4, plenty of light reaches the sensor in a relatively short exposure. This has several advantages from less demanding tracking accuracy, to being able to use a lower ISO setting.

The Downsides of this Lens

Now, I have to admit that up to this point, it sounds a little too good to be true. The downsides of this configuration are that shooting wide open can make focusing difficult.

The focuser adjustment ring on the Rokinon 135mm F/2 is excellent, but fine tuning your critical focus on a bright star at F/2 will take some trial and error to get right. You may need to refocus your subject as the temperature changes throughout the night.

You may need to stop down to control star bloat, and that’s exactly what I’ve done with this 135. I’ve set the f-stop to F/2.8, to sharpen up the stars a bit. In fact, in my test shots, I noticed that the red channel was a little softer than green and blue. To remedy this, I reduced the star size in post, and I started shooting at F/4 to really tighten things up.

Also, as creative as the wide field 135mm focal length is, it’s not practical for smaller DSO’s and most galaxies. Stick to Andromeda, and skip the Whirlpool.

I have heard others mention that this lens has a “plasticky” build quality, but I believe this aspect has been improved. The model I use feels solid and the barrel is constructed with metal.

The lens is not weather sealed, so you definitely don’t want to leave your camera and lens (and your tracking mount!) in the rain. There’s no image stabilization on the Rokinon 135mm F/2 either, but that’s a non-issue for amateur astrophotographers.

Recommend Astrophotography Targets for this Lens

I’ve captured a lot of deep sky astrophotography targets from the northern hemisphere, but I’m usually in too deep to capture an entire region of space at once. Here is a short list of great astrophotography targets to shoot at 135mm with this lens:

Orion’s Belt (Including the Horsehead Nebula, Orion Nebula, and M78

The Witch Head Nebula including Rigel in Orion (Careful with star reflection!)

Below, is an incredible example of the types of projects possible with the Rokinon 135mm F/2.0 lens. The following image was captured by Eric Cauble using the Samyang branded version of this lens.

The Sadr Region in Cygnus, including the Crescent Nebula by Eric Cauble.

Since Eric was so generous to share his images with me, I had to include his photo of the Rho Ophiuchi cloud complex as well. This photo was captured with the Samyang 135mm F/2 lens using a UV/IR cut filter and a QHY168C dedicated astronomy camera.

The Rho Ophiuchi Cloud Complex by Eric Cauble using the Samyang 135mm F/2 lens. See full-size version on Astrobin.

Final Thoughts

With an effective focal length of roughly 216mm when coupled with a Canon crop sensor body, the field of view is nearly identical to the one you’d find on a full frame camera with a 200mm telephoto lens. That’s quite a jump from 135mm, so the camera body you use with this lens may change the types of targets you shoot.

I can’t wait to try this lens out during the winter months on some wide field targets in Orion. The colder temperatures will make DSLR astrophotography much more practical, and there are plenty of great targets to choose from.

During the frigid months of winter, my motivation to spend over an hour setting up my complete deep sky imaging rig dwindles. However, stepping outside to polar align a small star tracker and attach a DSLR and lens is quick and painless.

In these situations, a portable, wide-field imaging rig wins.

Star parties or dark sky excursions are another great time to use a camera lens in place of the telescope. Not only does it let you travel light, but impressive wide field projects are often more successful when captured under a dark sky.

For those of you that like to “pixel-peep”, have a look at the single image frame captured using the Rokinon 135mm F/2.0 ED UMC at F/4. The image is a 90-second exposure at ISO 400 using a Canon EOS 60Da. The inset picture is a magnified view of the bottom right corner of the frame.

A single, 90-second exposure using the Rokinon 135mm F/2.0 ED UMC at F/4.

I hope that this post has provided some practical insight into a popular camera lens for astrophotography. If experience has taught me anything, it’s that the practical, pain-free equipment that gets the most use under the stars.

This lens is available on Amazon for most camera bodies. Make sure to select your camera mount when checking the price (Check current price). If you have pictures taken using the Rokinon 135mm F/2 lens, please feel free to share your results in the comments section (links to Astrobin, Flickr or your personal gallery are fine).

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The Impressive Optolong L-eNhance Filter

In this post, I’ll share my results using the Optolong L-eNhance filter for deep sky astrophotography in the city. The L-eNhance is a dual band pass filter that ignores artificial light, yet collects a strong signal emitted by certain nebulae.

This light pollution filter was designed for color cameras, whether it’s a DSLR (a modified camera is best) or a one-shot-color dedicated astronomy camera like the one used (ASI294MC Pro) for the images in this post.

As many of you know, I mostly shoot from the city. I love to travel to dark sky locations, but imaging from home is a lot more practical, and I can do it more often.

The problem is, the city I live in is home to over 100 thousand people, and that makes it very bright. Excessive light pollution is a reality for many of us, and I’m not sure we fully understand the long term negative effects of it yet.

The battle between light pollution and amateur astronomy wages on, but thanks to the organizations like the IDA, more people are aware of the situation and making small steps in the right direction.

Here’s a look at the light pollution I shoot through in my backyard. As you can see in this animated gif, it looks as though the light pollution increased significantly between 2018 and 2019.

For backyard astrophotographers like me, light pollution creates some serious challenges, from horrible gradient patterns, to a pathetic signal-to-noise ratio.

It seems like we have to work twice as hard as those under dark skies do to capture a beautiful image.

Fortunately though, light pollution filters exist – and the companies that make them are getting better and better at isolating the “good” light from the bad. The argument as to whether a light pollution filter for broadband targets (such as galaxies) can actually help you collect better data continues in the forums, but I have found them to make my life a lot easier.

However, nobody can argue the fact that a narrowband filter (often called “line filter”) can be exceptionally useful from the city. The filter I am discussing in this post is a dual-band pass filter, that collects light in two prominent emission lines, H-alpha, and Oxygen III.

The transmission graph of the Optolong L-eNhance dual-band pass filter.

Looking at the transmission lines of the band passes above, you may notice that this filter is only allowing a very selective amount of light to pass through to the camera. The good news is, some of the most incredible deep sky nebulae in the night sky emit the majority of their signal in these two wavelengths.

Which ones? The Eagle Nebula, Omega Nebula, and North America Nebula, to name a few. Emission nebulae are some of the most widely-photographed deep sky targets by amateur astrophotographers, and from a filter perspective, they are much more obtainable from the city than a broadband galaxy.

Optolong L-eNhance Filter

The Optolong L-eNhance filter was designed for color cameras, such as a a DSLR camera or one-shot-color astronomy camera. The camera used for all of the example images in this post is a ZWO ASI294MC Pro, a 10.7 MP 4/3″ sensor camera with cooling.

If you take a good look at the transmission graph, you’ll notice that the first band pass line includes both the OIII, and H-beta wavelengths. Essentially, this means that the filter should collect an even more “natural” looking image than one that isolates Ha and OIII exclusively.

The H-beta (486.1nm) emission line is nowhere near as impactful as the hydrogen-alpha line (656nm) when photographing an emission nebula target, but I like the idea of including this subtle wavelength for a more well-rounded image.

Transmission Lines

H-beta: 486.1nm

OIII: 501nm

H-alpha: 656nm

As you’ll see in the images shared in the post, this transmission combination leads to some surprising “natural” looking images when used with a color camera.

In the video below, you’ll see me use the Optolong L-eNhance filter for deep sky astrophotography in the backyard. Notice the bright white LED streetlamps that line my street. These artificial lights are largely ignored by the L-eNhance filter, as they do not emit light in the spectrum that passes through the filter.

In the video, I’ve threaded the Optolong L-eNhance filter (48mm version) to the field corrector of my Sky-Watcher Esprit 100 refractor telescope. The filter sits between the sensor inside my ASI294MC Pro color camera, and this apochromatic refractor telescope.

Threading the filter directly to the field corrector involves carefully removing the internal ring that seals the filter glass into the housing. The reason for this, is to access the threads on both sides of the filter. I do not recommend this method, as the filter glass becomes loose, and you could easily drop or damage the filter.

Instead, I would look into a filter drawer system that is compatible with your telescope. This allows you to easily swap filters in and out of the imaging train, and maintain the accurate spacing between your camera sensor and the corrector/field flattener.

The Optolong L-eNhance filter (48mm).

Some telescopes, such as the William Optics Zenithstar 73, or RedCat 51 include a threaded slot for a 2″ filter inside of the field flattener and/or adapter. This is a very convenient location for a 48mm filter, as it is completely sealed from the elements.

Optolong L-eNhance Filter Specifications

Here are the technical specifications of this filter, coming straight from the company. I have to admit, I don’t know what most of these terms mean, but in the spirit of creating the most useful resource possible, I’ve included them for those that do.

Blocking Range: 300nm – 1000nm

Blocking Depth: >99% light pollution line

TPeak: T>90%

Substrate: B270

Thickness: 1.85mm

Surface Quality: 60/40

Transmitted Wavefront RMS: λ /4

Parallelism (arcsec): 30s

If you don’t know what the transmitted wavefront RMS reading means in terms of the pictures you can expect to capture with your color camera, keep reading…

Imaging Results from the City

The first object I chose to photograph was the Butterfly Nebula, which is also found within the Sadr region in Cygnus. The reason I chose this target for my my testing, was because this area is absolutely loaded with emission nebulae. If you have a filter that specializes in isolating H II regions, this is an area of the night sky you need to photograph.

Having used a dual band pass filter in the past (STC Optical Du0-Narrowband) from my backyard, I had a feeling that the L-eNhance would meet my expectations. I primarily shoot using a color camera, to maximize the chances of completing an image in a single night. If you are like me, a dual band pass filter may be the answer you are looking for.

In the past, I have used a number of Optolong branded filters, including narrowband “line” filters for Ha, OIII, and SII. The Optolong L-Pro is one of my favorite brpad-spectrum filters, so my experiences with this company have been stellar thus far. (They even sent me an Optolong Flag for my garage as a thank you for my video content!)

Results using a 100mm Refractor Telescope

The first image was captured using a high-end refractor telescope (ED triplet apochromat), with a focal length of 550mm. The image scale of this system is 1.7, which creates a pleasing resolution for wide-field nebulae targets like the one below. To find out the image scale of your camera and telescope, you can check out this online calculator.

With a dual-band pass filter like the L-eNhance, moonlight, and the glow of my city do not interrupt a memorable imaging session in Cygnus. Below, is the image I captured using the L-eNhance filter with my ZWO ASI294MC Pro (one-shot-color) camera. The final image includes 69 x 4-minute exposures for a total integration of 4 hours and 36 minutes.

The Butterfly Nebula in Cygnus. 69 x 4-minutes.

If you would like to see all of the equipment used for this shot, I have broken everything down piece-by-piece on this page.

Below, you’ll see a breakdown of what the data looks like in each color channel, after the image has been processed and balanced as the version above. Although these images are non-linear, it should give you a better idea of how much data was collected in each color after neutralizing the background.

The “stretched” image (the one shown above) shows exaggerated levels of data, but it does indicate the general level of sensitivity to color in each channel.

After an extremely successful night using the L-eNhance filter on my 100mm refractor, I thought it would be interesting to see what would happen when I use it on the Celestron 8″ RASA.

Results using the Celestron 8″ RASA

To use this filter with a Rowe-Ackermann Schmidt Astrograph system, it must be placed in front of the camera sensor that sits on the corrector plate of the front of the telescope. To achieve the correct spacing between my camera sensor and the optical window of the RASA, I use this Starizona filter drawer.

I also installed a new Pegasus Astro FocusCube 2 motorized focuser to the RASA, for imporved accuracy when focusing this demanding F/2 optical system. The one I have was designed specifically for Celestron SCT telescopes and the RASA (This is the model I use).

As fast as the F/2 f-ratio of the RASA is, it also means that achieving critical focus manually is very difficult. I believe that relying on camera control software to measure the accuracy of your focus precision is a must.

Which software? Many amateur astrophotographers have had success using Sequence Generator Pro, and I personally use Astro Photography Tool. The FWHM or HFD readings of a star are needed when attempting to find (and maintain) critical focus (More on this in a later post).

Here is a better look at the FocusCube 2 installed on the RASA. The process involves removing the standard focus knob on the telescope, and attaching a bracket to the base. I’ll share a new video and review of this focuser for the Celestron RASA soon.

To highlight the qualities of this filter on a telescope like the RASA, I decided to hop over to the Omega Nebula in Sagittarius. From my latitude in Canada, I have a very short window of opportunity to photograph this target. It does not reach a high apparent altitude in the sky, which makes it a demanding target for amateur astrophotographers in the Northern US or Canada.

As you’ll see in the image below, the images straight out of the camera will appear green using CMOS camera like the ASI294MC Pro.

To create the final image, each sub-exposure was 3.5-minutes in length, with the camera set to Unity Gain. For this image, I also used autoguiding with the RASA as well (for the first time). I attached a small 50mm guide scope (Starfield 50mm guide scope) and bracket to the base of the 8″ tube.

The biggest advantage of having an autoguding system in place with the RASA (in my opinion), is the ability to dither between frames. In previous imaging sessions with the RASA, I had no trouble capturing unguided images with round stars on the Celestron CGX-L. However, walking noise was prevalent due to a lack of the simple (yet powerful) act of dithering.

The Omega Nebula. Color CMOS camera with Optolong L-eNhance filter.

When it was all said and done, I ended up with 29 x 210 second exposures on the Omega Nebula through the 8″ RASA. As you can see in the processed image stack above, achieving a “near-natural” looking color balance with this dual band pass filter is possible. I can’t help but think that the additional light collected in H-beta makes a subtle, yet important difference on targets like M17.

I also pointed my telescope towards the Helix Nebula using this filter. This planetary nebula in Aquarius is another deep sky object that does not reach a high apparent altitude in my night sky. The L-eNhance filter did a fantastic job of separating the glowing gases of NGC 7293 from a light polluted sky.

The Helix Nebula. ZWO ASI294MC Pro + Optolong L-eNhance Filter.

L-eNhance vs. STC Optical Duo-Narrowband

Many readers have asked how the Optolong L-eNhance filter compares to the STC Optical Duo-Narrowband filter. In my tests, it produces VERY similar results when used an emission nebula. If you look at the transmission graphs between the two, you’ll see why.

The L-eNhance lets in a subtle amount of light in the H-beta line, which I am yet to illustrate how much of a difference this makes. The transmission peak in the OIII spectrum also appears to be wider, which may help produce a more natural looking image (at the expense of less isolated data).

The bottom line is, these filters act very similar, and I don’t own equipment sophisticated enough to truly show the difference between the transmission qualities of this glass. In reality, I think most folks just want a filter that compliments their color camera when shooting in the city, or under moonlight. If that is what brought you here, I think you’ll be extremely impressed with the Optolong L-eNhance.

What others are Saying…

I’m not the only one seeing great results with this filter. Ron Brecher is one of my favorite astrophotographers, and someone I look up to personally in terms of his work and his career. He uses sophisticated imaging equipment from his observatory in Canada (only 2 hours from me!) to capture stunning deep sky objects. He shared this image on his website, and on twitter about the Optolong L-eNhance filter:

The image was captured using a QHY 367C one-shot-color camera through a Tak FSQ-106. Be sure to visit Ron’s website to see the full size version of the image, it’s really incredible!

Final Thoughts

Narrowband filters, especially ones that collect light in two band passes at once offer an incredible way for backyard astrophotographers to collect impactful images with a color camera. Whether you shoot with a DSLR or dedicated astronomy camera, a capable light pollution filter can be the difference between setting up twice a week, and twice a season.

There is no substitute for dark skies, but there is hope your light polluted backyard. The Optolong L-eNhance filter took months to develop, and as you can see first hand from my images, the results are impressive.

I you have used the Optolong L-eNhance filter with your color astrophotography camera, please let me know what you thought in the comments. Feel free to include a link to your personal website or AstroBin profile to share an image captured with it. Seeing others work is a great way to validate the performance of this filter.

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Sky-Watcher EQ6-R Pro Review

The Sky-Watcher EQ6-R Pro is a computerized equatorial telescope mount with GoTo capabilities. This equatorial (EQ) mount is capable of providing precise, accurate tracking of the night sky, and is suitable for long-exposure astrophotography.

The core specifications of this equatorial mount include having a built-in ST-4 autoguider port, a payload capacity of 44 pounds, and a SynScan computer hand controller with an extensive database of objects.

I have been using the Sky-Watcher EQ6-R Pro telescope mount since October 2018, and have used it to capture several deep sky images of nebulae, galaxies, and star clusters in space. In this post, I’ll share some of my favorite features of this EQ mount that I have experienced over several imaging sessions in the backyard.

Whether you already own the EQ6 and are looking to tap into more of its features, or are trying to decide which equatorial mount is best for your visual observation or astrophotography goals, this article should offer up some useful input from someone who’s been in your shoes.

The Veil Nebula captured using the EQ6-R Pro telescope setup shown on the right.

Sky-Watcher EQ6-R Pro Review

Before we dive into some of the interesting features you may not have known about, here is an overview of exactly what the “EQ6” is capable of. As a preface, it’s worth noting that I use this mount for astrophotography exclusively, and I am in the northern hemisphere.

For those in the southern hemisphere, the process is very similar all around, aside from polar aligning the mount with the south celestial pole (SCP).

Before stepping up to the EQ6-R, I used a number of intermediate level astrophotography mounts, including the slightly smaller HEQ5 Pro SynScan model.

The Basics

The EQ6-R Pro includes a SynScan hand controller with an LCD display that gives you control it’s features and basic functions. The left and right keys on the keypad control the Right Ascension (RA) axis, while the up and down arrows are used to control the Declination (DEC) axis.

You can control the slew speed by selecting the RATE shortcut button (2) on the keypad, as it is useful to make large movements at a high speed, and subtle adjustments using a slow speed. The Sky-Watcher EQ6-R Pro has 10 slew speeds for complete control over the movement of each axis.

Before powering up the EQ6-R, your telescope should be in the home position. This means that the EQ head is leveled on the tripod, and the RA axis is pointed towards the north celestial pole (NCP). The counterweight should be at its lowest position, and the telescope should be pointing towards the NCP. You can then turn on the mount and select the operation mode.

For those interested in astrophotography, you will only ever want to use the mount in EQ mode.

The Iris Nebula in Cepheus captured using the setup shown on this page.

With the RA and DEC clutches locked, and counterweight(s) attached, you can mount your telescope on top of the EQ head. This is accomplished by fastening the mounting plate of your telescope to the saddle, which accepts both D and V-style mounting plates.

Getting Started

Once the SynScan system has initialized, you can enter in the geographic coordinates of your observing site.

This involves entering the latitude and longitude coordinates of your current location using the cursor on the LCD display and the keypad. Then, you will enter in your current time zone, which for me, happens to be UTC -4 in southern Ontario.

You can also enter in your current elevation, which which is used for atmospheric refraction compensation (generally, the higher your elevation, the better). Next is setting the current date and time, and whether you are currently on daylight savings time.

Once all of these important details have been entered (so the mount understands what is available in the sky from your location), you reach the mount alignment process, with the “Begin Alignment” dialog served up on the LCD screen.

The SynScan Hand Controller set to EQ Mode.

Use the “Park” Feature

This simple, yet useful feature automatically aligns your telescope mount in both axis at the beginning of your imaging session. It is not exclusive to the EQ6-R Pro, yet it is easy to miss if you don’t follow the instructions in the manual on your first few runs.

This feature is located under the “Utility Function” menu and asks you to turn off the mount after the park position has been confirmed. The next time you turn the mount on, you will see a dialog on the LCD display asking if you would like to start from the park position.

This is a handy feature that I did not personally take advantage of for the first few months of ownership with the mount. It is nice to confirm the home position when setting up, especially before beginning your polar alignment process.

The EQ6-R is Easy to Polar Align

Whether you use the built-in polar scope with the illuminated reticle, or use a QHY PoleMaster device, polar aligning the EQ6-R is a breeze.

This largely due to the fact that the EQ6-6 includes large, Alt/Az adjustment bolts with comfortable handles. Fine tuning the polar axis of this equatorial telescope mount is possible thanks to these convenient controls.

The built-in polar finder scope with illuminated reticle allows you to accurately polar align the mount without the need for additional software or accessories. You can either use a third party mobile app like “Polar Finder” to find out the current position of Polaris, or simply use the information displayed on the SynScan hand controller.

The SynScan hand controller displays the position of Polaris in polar scopes field of view (FOV). You need to imagine that the large circle in the FOV of the polar scope as a clock’s face with 12:00 sitting at the top.

Then, it’s simply a matter of adjusting the Alt/Az bolts of the mount to place Polaris in the “HH:MM” position provided.

Using a PoleMaster with the EQ6-R

If you don’t like getting underneath the polar scope for a real time view of the NCP or SCP, the QHY PoleMaster is a great option. This electronic polar scope uses a small camera to display the region surrounding the north (or south) celestial pole.

Using the live feed through the camera, you can fine tune your Alt/Az adjustments in a very precise manner. The PoleMaster requires the appropriate adapter (this is the one you need) to fasten it to the polar axis.

Fastening the PoleMaster to the EQ6-R using the necessary adapter.

You Can Improve the Alignment Accuracy

Before running a star alignment routine, make sure that your telescope is well balanced, and that there are no loose cables that could get caught and snag on the mount.

The alignment routine involves choosing a bright, named star from the database and centering it in your telescope eyepiece or camera. The LCD screen displays “Choose 1st Star”, at which point you can cycle through the list to find a star that is not blocked by any obstructions from your location, and press enter.

A word of caution here, once you hit enter, the mount will start to slew to the object immediately.

From here, it’s a matter of using the arrow buttons on the keypad to center the star. Remember, you can change the slew speed at any time by pushing the “Rate” button and setting the value higher or lower. It is often useful to leverage a finder scope on your telescope when slewing to your first alignment star, as it has a much wider field of view than your primary telescope and makes finder the first star easier.

When running through a star alignment routine, it is important to consistently center the alignment star in the eyepiece or camera’s FOV. It is beneficial to use a reticle eyepiece with a small FOV. Personally, I use the camera’s FOV and center the star on my DSLR display screen (with grid enabled), or with a cross-hair overlay in my camera control software (Astro Photography Tool).

You can run a 1,2, or 3-star alignment to improve the pointing accuracy of the telescope. This is very important when it comes to photographing deep sky objects that are nearly invisible until a long exposure image is collected.

The Tulip Nebula in Cygnus using the EQ6-R Pro mount for tracking.

Avoid Errors due to Mechanical Backlash

You can improve your alignment accuracy by avoiding errors due to mechanical backlash. Backlash is present in all equatorial telescope mounts, and does not affect your observing enjoyment, or your long exposure images when autoguiding is employed.

To avoid introducing alignment error caused by backlash, center the alignment star ending with an UP and RIGHT directions from the keypad. If you overshoot the star using this method, use LEFT and DOWN to bring the star back down the FOV and try again.

The Stepper Motors are Quiet

If you haven’t used this particular mount first hand, you may be wondering what the EQ6-R sounds like while it is slewing. I have heard many astrophotography mounts over the years, and this one is impressively quiet.

This mount uses stepper motors with a 1.8° step angle and 64 micro steps driven. This technical design aspect results in a quieter mount than on using servo motors.

This means that even at the maximum slew speed (9X), the mount emits a modest hum that will not wake up your neighbors. While the telescope mount is tracking, it is completely silent. It’s only when you move the RA or DEC axis at top speed that you hear a noise.

Compared to other equatorial telescope mounts I have used, the audible sound the EQ6-R Pro makes is more than acceptable. When you are partaking in a hobby that takes place (alone) outside at night, avoiding loud or unusual noises when possible is always a good idea.

In contrast, the Celestron CGX-L computerized mount is noticeably loud while slewing at top speed. If this mount is being used in a closed observatory, it’s not an issue. However, I set up my equipment in a city neighborhood backyard. Depending on the time of night, I hesitate slewing to a new target because of this trait.

The Autoguiding Performance is Impressive

The Sky-Watcher EQ6-R Pro delivers impressive results when the built-in autoguider port is leveraged. Over the years I have maximized the tracking capabilities of my astrophotography mounts by using an auxiliary guide scope and camera to autoguide using a free software called PHD2 guiding.

The EQ6-R Pro allows you to set change the default auto guide speed of the mount of 0.5X to 0.75X or 1.0X in the setup menu.

I have experimented using a guiding rate of 1.0X , and saw little improvement to my guiding graph in PHD2 guiding over the default speed of 0.5X. The point is, you have the option of adjusting this setting if the need calls for it, and it’s a feature I’ve only recently tapped into on the EQ6-R Pro.

For a real-life example of the autoguiding performance you can expect with this mount, have a look at the screenshot below. The guiding graph shows that my total RMS error is 0.63″. Generally, a total RMS error of under 1-second means that you can expect pin-point stars in your long exposure images.

The Mount is Heavier Than it Looks

When it comes to equatorial mounts for astrophotography, being heavy is a good thing. However, I think some people that receive their EQ6-R for the first time may be a little surprised at how heavy the EQ6-R actually is (I was).

The weight of the EQ head is 38 lbs on it’s own, and the tripod adds another 16.5 lbs. Add in two 11-lb counterweights, and you’ve got a telescope rig that weighs 76.6 pounds, and is not going anywhere for a while.

Luckily, the EQ head includes a useful carry handle that I have certainly put to good use. Also, the supplied counterweight bar is retractable, which makes transporting the mount out the door of my garage a little easier.

I used to carry my Sky-Watcher HEQ5 Pro SynScan around the yard with the telescope and counterweight attached. It was heavy and awkward, but manageable.

This is not possible with the EQ6-R, which is understandable considering the increased payload capacity (44-lbs) of the mount. To transport the Sky-Watcher EQ6-R from my detached garage to the yard, I must remove the counterweights and the telescope first.

It’s possible to lift the tripod with the EQ head attached (54.5 lbs), but this is likely too heavy for most folks. The good news is, this heavy profile means that accidentally bumping the polar alignment out of position by kicking a tripod leg is unlikely. Smaller, ultra-portable mounts like the iOptron SkyGuider Pro do not share this quality.

You Don’t Need to “Mod” the Mount

If you’re a tinkerer, I get it. It may be tempting to you to open up the EQ mount head and take a look. I would advise against this personally, as you may do more harm then good.

I’ve seen a number of posts and videos discussing “belt-mods” and “hyper-tuning” Sky-Watcher NEQ6 and EQ6-R mounts. Personally, I wouldn’t recommend opening up the mount in hopes of tweaking performance, even if the underlying mechanics are straightforward to you.

In my experience, the Sky-Watcher EQ6-R can track accurately for 10-minute exposures (or longer) without any re-greasing or modifications to the worm gears when autoguiding is leveraged.

I suggest spending the time to get your balance and polar alignment spot-on before blaming the mount for bad tracking. It’s easy to get caught up in scrutinizing the mechanical backlash and periodic error present in the mount.

If you do dive into these advanced adjustments, you better be mechanically minded and ready to invest a “minimum of four hours” for a typical belt modification.

The EQ6-R with a Sky-Watcher Esprit 100 ED APO attached.

The SynScan Hand Controller gives you Extensive Options

The included SynScan hand controller includes an impressive 42,000+ object database, with almost every possible target you could ever want to observe or photograph.

The Messier object list gets a lot of use for amateur astronomers in the Northern Hemisphere, while the NGC catalog is great for pointing the telescope at more obscure nebulae and star clusters.

The database also includes IC and Caldwell catalogs, which covers most of the noteworthy subjects in the night sky. I only wish the database included the Sharpless catalog, for items such as the Tulip Nebula with no alternative designation.

To slew to these objects, it may be better to control the EQ6-R using your PC using supplementary PC-Link cable along with the appropriate ASCOM drivers and software.

I use the hand controller to align, and center my target. After a quick polar alignment routine using the QHY PoleMaster, the pointing accuracy of the mount is spot-on using just a 1-star align.

After you’re aligned and ready to observe or image an object in space, you can start by choosing a target using the “OBJECT” shortcut key, which contains the following object list:

Named Stars

Solar System

NGC Catalog

IC Catalog

Messier Catalog

Caldwell Catalog

SAO Catalog

Double Stars

Variable Stars

User Object

Deep Sky Tour

The deep sky tour is a very cool feature for visual observation sessions. Imagine a star party or public outreach event where you want to have the best list of targets at the ready.

This feature generates a list of the most famous deep sky objects that appear in the current night sky overhead. You simply go through the list and pick them off one by one.

The Periodic Error Correction (PEC) Feature

Periodic tracking error is present in all equatorial telescope mounts, and is a due to the design of the internal gears. The Sky-Watcher EQ6-R includes a periodic error correction (PEC) function to help correct this.

The PEC training procedure requires that you first polar align and star align the telescope mount. Then, slew to a star close to the celestial equator, and center it in the telescope eyepiece or imaging camera.

Then, navigate to the Utility Function > PEC Training mode and press enter. From here you can select the speed you would like to use for PEC training. The Sky-Watcher SynScan manual suggests using 0.125X sidereal rate for wider FOV telescopes such as the Esprit 100 ED APO.

After selecting the speed using the “1” or “2” keys, the screen will then start to display the elapsed time of the PEC training routine. Now, your job is to keep the star centered in the FOV using the left and right direction keys on the hand controller.

Once the PEC training routine has completed, the elapsed time will stop. Noe, you can select “PEC+Sidereal” as a tracking speed in the Setup menu. It is recommended to wait for at least one PEC training reply cycle to complete before you start taking your images.

Power Supply for the Sky-Watcher EQ6-R Pro

As one Cloudy Nights forum member put it, the Sky-Watcher EQ6-R Pro can get “cranky” if the right power supply is not used. I have experienced this issue myself, when I used an AC to DC power adapter that did not provide a minimum 4 amps of power.

These days, I use a 12V AC/DC adapter with 10 amps to power the EQ6-R when plugged in at home. Here is a picture of the exact AC/DC adapter I use with the EQ6-R, and here is a link to it on Amazon. Others have found the Pyramid PS9KX 5 Amp power supply to work well with this mount.

The AC/DC adapter I use to power the EQ6-R Pro mount from home.

Final Thoughts

As you may have noticed, there is a lot to cover when discussing all of the features of the Sky-Watcher EQ6-R Pro SynScan computerized telescope mount. The very first night I used the EQ6-R, I captured one of my favorite astrophotography images to date, and I knew I was in a for a long relationship with this mount.

A reliable equatorial mount is the foundation of every great deep sky astrophotography kit, and the EQ6-R is a worthy investment for those looking for a stable, long-term solution for long-exposure imaging.

From my early days with the HEQ5 Pro to my latest session in the backyard with the EQ6, I’ve been extremely satisfied with the user experience and performance of Sky-Watcher’s affordable equatorial telescope mounts.

Pros:

Fantastic Tracking when Autoguiding Used

Quiet Stepper Motors even Slewing at 9X

Easy to Polar Align

Built-In PEC Training Feature

Cons:

Heavier Than it Looks

Intermediate Level Mount with Price to Match

Power Supply must be Correct or will Act Up

What Others Have Said:

“This mount is simply amazing. It is robust and tracks very well. I was taking 5 minute subs with no star trails. It is built like a tank and handles my Meade 5″ refractor with ease. The stepper motors are quiet. It’s simply a joy to use and I highly recommend it. The price is well worth it” – James S. on HPS website

“This mount is a tank. I have been doing astrophotography for several years using a lighter weight mount but I was ready to setup up to a heavier payload mount and I am very pleased.” – Ray on HPS website

Useful Resources:

Do you use the Sky-Watcher EQ6-R Pro for astrophotography? If so, let me know your experiences with it in the comments. To stay up to date with my latest adventures in the backyard, be sure to subscribe to my newsletter. Until next time, clear skies!

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QHY PoleMaster Review

The QHY PoleMaster electronic polar scope was designed to make your polar alignment routine easier, and more precise. No matter which camera tracker or telescope mount you’re using, when it comes to astrophotography, accurate polar alignment is critical.

If you have ever struggled to polar align your telescope mount with the north or south celestial pole, the QHY PoleMaster may just be your new best friend. With a slew of recent technical headaches and an unforgiving winter, my appreciation for devices that make my life easier has grown.

The QHY PoleMaster delivered exceptional results for me on my first night out with it. The dedicated polar alignment software was easy to use, and the camera produced a crystal clear image of the star field surrounding the north celestial pole.

I experienced that cliche moment I expect all backyard astrophotographers had with this device their first night where I thought, “I should have been using one of these a long time ago”. It’s true.

The PoleMaster I am using is for my Sky-Watcher EQ6-R Pro EQ mount, and I have fastened it to the mount using the dedicated QHY adapter for this model.

QHY PoleMaster Review

In this post, I’ll review the QHY PoleMaster from the perspective of an experienced amateur backyard astrophotographer who’s spent a lot of time manually polar aligning mounts using polar finder scope.

When others would mention the QHY PoleMaster to me, I would say that I just don’t need one. I felt comfortable manually polar aligning my telescope mounts and camera trackers, from the iOptron SkyGuider Pro, to the Sky-Watcher EQ6-R Pro.

My deep sky astrophotography setup with a PoleMaster fastened to the polar axis of the telescope mount.

I use a mobile app (Polar Finder) that gives me a readout of the current position of the north celestial pole, and fine tune the altitude and azimuth controls of my mount to line the axis up as best as possible. On the Celestron CGX-L, I have the All-Star Polar Alignment feature to help me out.

So why do I need a QHY PoleMaster to aid me in this process? Because sometimes “as best as possible” just isn’t good enough. Oh, and kneeling on the cold pavement or wet grass to get behind that polar scope kinda sucks too.

What about confirming the position of Polaris in the illuminated reticle after I’ve started imaging? Depending on the angle my telescope is pointed (on the EQ6-R), this simply isn’t an option. In fact, there is a long list of benefits to using the QHY PoleMaster over a manual alignment routine that I seemed to have ignored up until now.

I can polar align faster, at dusk

My old method of polar alignment was fast, this one is faster. I no longer need to wait until I can see Polaris with my naked eye to get started.

I don’t have to get on the ground

I like to leave my telescope mount tripod legs at their minimum height for maximum stability. However, this makes getting underneath the polar scope tricky and somewhat painful (I feel old).

Improved polar alignment accuracy

A high precision camera can achieve a higher level of polar alignment accuracy than “my best try”. The imaging camera in the PoleMaster has a resolution of 30 arc seconds.

I can monitor and confirm my polar alignment at any time

Any slight amount of drift due to bumping the mount, sinking into the lawn or other factors I had no way of monitoring are now easy to identify and fix.

No more 3-star alignment routines

Why didn’t someone tell me about this feature? The spot-on accuracy of the PoleMaster means that only a 1-star alignment routine is needed for your telescope mount to learn the sky.

The pointing accuracy of your telescope mount will vary depending on the focal length of the telescope you are using for astrophotography.

Eliminating any cone error in your telescope mount will improve your pointing accuracy even further. The Sky-Watcher EQ6-R Pro has an option to adjust this.

QHY PoleMaster EQ Mount Polar Alignment Camera Specifications:

Field of View: 11 degrees by 8 degrees

Interface: Mini USB 2.0

Resolution: Approximately 30 Arc seconds

Weight: 115 g (0.25 lb)

What’s included in the box

This PoleMaster was sent to me from High Point Scientific for review. The team at High Point made sure to include the necessary adapter for my EQ telescope mount. Here is a look at everything that comes with the PoleMaster:

PoleMaster camera body

Lens cap with a lanyard

Mini USB 2.0 cable

Mount adaptor

Mount adaptor cap

M4 hardware for attaching the adaptor

Allen key for lens focus adjustment

When ordering your PoleMaster, make sure to specify which mount adapter you need for your specific telescope mount.

Fastening the PoleMaster to your telescope mount

The PoleMaster I am using is for my Sky-Watcher EQ6-R Pro EQ mount, and I have fastened it to the mount using the dedicated QHY adapter for this model. The hardware was easy to install, and the materials used and overall finish of this device is attractive.

The adapter for my Sky-Watcher EQ6-R came with a tiny Allen key to adjust tension, so I could securely lock the PoleMaster into the front of the polar axis scope of the mount. The adapter I am using for the Sky-Watcher EQ6-R also works with CGEM style mounts from Celestron.

The QHY PoleMaster adapter for the Sky-Watcher EQ6-R

There are two parts to the mount adapter for the PoleMaster, the camera base disc that attaches to the camera body, and the camera mount ring that you need to secure to the mount. You secure the camera base disc to the mounting ring using a thumb screw.

For the EQ6-R mount adapter I used, there were three tiny grub screws to tighten using the supplied Allen key to lock the adapter into place.

I have also mounted the PoleMaster to a Celestron CGX-L telescope mount using a Celestron ADM adapter. The adapter clamps to the dovetail bar of the imaging telescope (In the example below, an 8-inch RASA). This adapter worked exceptionally well when polar aligning the Celestron CGX-L for imaging without the use of autoguiding.

The PoleMaster mounted to a Celstron CGX-L mount and RASA telescope using an adapter.

The device connects to my PC via a Mini USB 2.0 cable, with miniature locking screws to avoid yanking the cable out by accident. I wish more of my device connectors had this. The manual instructs you to position the USB port of the PoleMaster to the left hand side when looking at the device head on.

I ran the mini USB 2.0 cable from the PoleMaster into my recently upgraded powered USB hub, which consolidates the various astrophotography devices I have running to a single USB cable into my laptop.

The adapter allows you to take the PoleMaster off of the mount while not in use or in storage, but I think I’ll leave it right where it is. The tiny camera adds no weight to my rig and maintains a low profile.

I’ll just have to make sure I don’t bang anything against the device by accident when setting up. The included lens cap should stay on the PoleMaster when not in use to protect the lens.

There are several adapters available for the PoleMaster to fit with your specific telescope or camera mount. From small camera trackers such as the Sky-Watcher Star Adventurer, to monster mounts like the Celstron CGX-L. Be sure to speak with the vendor about which adapter you need for your mount.

For mounts like the Celestron CGX-L that do not have a polar axis scope in the mount, a specialized L-bracket and adapter is needed to mount the device. In the photo below, you’ll see how I have mounted the PoleMaster underneath the dovetail rail of the 8″ RASA F/2.

The PoleMaster mounted to the CGE dovetail rail of the Celestron RASA.

Looking for a dedicated electronic polarscope for the iOptron SkyGuider Pro? If you haven’t found an adapter to mount the PoleMaster to this mount, consider the iOptron iPolar device. The iPolar and adapter were made specifically for the iOptron SkyGuider Pro.

Software and Downloads

All of the software and drivers needed to run the PoleMaster device were found on the QHY website. The company has recently updated their site, which lead me on a bit of a wild goose chase.

Rather then using the URL printed on the green card that came with the camera, I simply “Googled “QHY PoleMaster Driver” to find the appropriate section of the QHY website.

Here, I downloaded the latest stable driver for the PoleMaster, along with the dedicated software needed to communicate with the camera and control parameters such as gain and exposure length.

With the 2 downloads unpacked and installed, I ran the PoleMaster software on my field laptop with the camera connected. The QHY PoleMaster manual (link below) was to-the-point and helpful through this process, and instructed me to click the “connect” button.

I heard the reassuring “new device connected” chime on my Windows 10 OS after plugging in the PoleMaster, so I new the camera was successfully recognized by my PC.

Tip:

If your PC has trouble recognizing astrophotography accessories and devices, I recommend unplugging the device and reconnecting to a new USB port. Monitor the Windows device manager to troubleshoot any connection issues.

After hitting the “connect” button, the PoleMaster delivered a live-view loop of the stars in the northern sky. The mount was already roughly polar aligned to my latitude at 43 degrees north, and pointed in the general direction of Polaris in my backyard.

The PoleMaster camera lens has an 11 x 6 degree of field of view. This means that the pole star should be visible if the mount has been roughly polar aligned.

Even though it was not completely dark out yet, I could see a formation of stars in the display screen right off the bat. After zooming out to 75% view, the north star, Polaris was obvious.

Us northern hemisphere folk have the luxury of having a bright pole star. In the southern hemisphere, the PoleMaster Uses Sigma Octans as a reference, which is a bit trickier to identify.

Using the PoleMaster Software

The PoleMaster software user interface.

The first thing you’ll want to do is adjust the gain and exposure settings so that it is easy to identify the pole star and a number of adjacent stars in the field.

The software walks you through a simple process of identifying and confirming the pole star. The process involves matching an overlay of star positions with your current view of Polaris and surrounding stars.

The rotate tool on the left hand sidebar lets you rotate the star pattern overlay using your mouse or trackpad to line up with your current live view of the north star.

Then, you are asked to rotate the RA axis of your telescope mount to determine the rotation of the mechanical axis. By rotating your mounts right ascension axis by 15 degrees or more, the software can confirm this value.

I made the mistake of releasing the RA clutch of the mount to perform this step, when the manual clearly states that this must done using the hand controller or mount control software such as EQMOD.

The reason for this specification is that by releasing the RA clutch, you shift the rotational center of the mount. Instead, keep the RA clutch locked, and perform this rotation by pressing the east button on the keypad.

Next the on-screen prompts tell you to confirm the center of rotation. Eventually, you will get to a point where the application displays a small green circle. This is exactly where the pole star needs to be. At this point, the ultra-fine adjustments you make to your polar alignment are far beyond what’s possible with the naked eye.

I wonder how far off the north celestial pole I was in the past?

Aligning the polar axis of my telescope mount with the true north celestial pole using the PoleMaster.

Atmospheric Refraction

The PoleMaster has an option to enable a feature called atmospheric refraction to further improve your polar alignment accuracy. This feature asks you to input your coordinates, temperature, and pressure. For atmospheric refraction to work correctly, the USB connector on the PoleMaster must be facing east.

Owners of the PoleMaster have recommended to start the polar alignment routine with your telescope to the west instead of the home position. 2 moves or more than 30 degrees can be difficult from the home position, so if the telescope starts in the west it is not an issue.

If you do not remove the PoleMaster from your telescope mount between astrophotography sessions, you can reuse the centering procedure from your previous polar alignment. However, if you are using the atmospheric refraction feature, you’ll need to remember to adjust the temperature and pressure settings for that night.

PHD2 Drift Alignment for Improved Accuracy

Some amateur astrophotographers has found that by using the drift alignment tool in PHD2 guiding, you can improve your polar alignment accuracy even further with the PoleMaster. The drift align tool in PHD2 works by measuring the error (drift) of a star, and adjusting the mount to reduce the error.

You repeat the process of measuring the drift error and adjusting the mount by adjusting the altitude and azimuth bolts until the drift error is as close to zero as possible. Because this feature of PHD2 gives you a way to measure the amount of drift error in your polar alignment, it can be a useful way to really dial in the accuracy of your polar alignment that you have determined using the PoleMaster.

I have never went to these lengths to confirm the preciseness of my polar alignment myself, but if you are interested, you can watch this presentation on the Astro Imaging Channel. For those that are setting up a permanent observatory, I can see how this level of accuracy justifies the commitment of time.

My photo of the Pinwheel Galaxy using the QHYCCD PoleMaster for polar alignment on the Celestron CGX-L mount.

Final Thoughts

There is a reason so many amateur astrophotography enthusiasts own a QHY PoleMaster. Whether you want to improve your polar alignment accuracy, save time, or ditch those 2nd and 3rd alignment stars when setting up – the PoleMaster can make your time under the stars more efficient.

The pressure and urgency to capture images increases when you have a limited window of clear sky time. When even a single aspect of your astrophotography setup is off, you can quickly squander your night sky bounty for the night.

Devices like the QHY PoleMaster help to optimize your imaging experience and allow you to focus on the photography side of things, like collecting images. The peace of mind knowing that your telescope mount is optimized for the apparent rotation of the night sky is one aspect of the hobby every one of us can appreciate.

At under $300 USD for the QHY PoleMaster Electronic Polar Scope is an obvious upgrade to any amateur setup, whether you think you need one or not. Is it possible to get your rig accurately polar aligned without the PoleMaster? Sure.

But in a hobby where little things make the difference between a good image, and a great one – I like to take every advantage I can get.

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ZWO ASI294MC Pro Review

The ZWO ASI294 MC Pro is a remarkably capable one-shot-color CMOS camera for deep sky astrophotography. Whether you use it for broadband true-color images on a moonless night or ultra-long-exposure images using your favorite narrowband filter – this camera can produce insanely beautiful images.

This is easily one of the best color cameras I have ever used for astrophotography, and my go-to choice for a night of deep sky imaging. Over the past year, I have used this camera extensively through a number of telescopes in the backyard and beyond.

Here is a taste of what the ASI294MC Pro can do:

The Trifid Nebula using a Luminance Filter with the ASI294 MC Pro

This photo of the Trifid Nebula was captured using the ZWO ASI294MC Pro with an Astromania Luminance filter (IR Cut) in front of the sensor. The photo was captured under the dark skies of the Cherry Springs Star Party in 2018.

The ASI294MC Pro has proven to be an incredible 4/3 sensor CMOS astronomy camera in the astrophotography community. This camera is responsible for my best deep sky images to date, including the photos shown below.

It is the best camera I have ever personally used for astrophotography, and I continue to use it to this day. At under $1K (US), you’ll be hard pressed to find a more versatile, reliable, and easy-to-use color astronomy camera.

This camera works exceptionally well with broadband light pollution filters, and narrowband filters. Many people will advise you not to use a color camera with narrow bandpass filters such as H-alpha or OIII, but I have found the 294MC Pro to perform extremely when used with a duo-narrowband filter.

If you want to see what others are doing with the ASI294MC Pro, have a look at the #ASI294MCPro hashtag on Instagram, and you’ll see that it’s not just me. You can also see exquisite example images with this camera on Astrobin.

ASI294MC Pro Astrophotography Camera Review

I can safely say that I now know exactly what the ASI294MC Pro is capable of, and some recommended settings that you can use for a successful image. I’ve used this camera for both full-color images with light pollution filters, an IR cut filter and narrowband filters that separate certain wavelengths of light such as Ha and OIII.

This OSC (One-shot-color) camera performs exceptionally well in both situations. The idea of capturing narrowband images with a color camera is something that is generally advised against in the astrophotography community. This is because a color sensor will essentially record about one-quarter of the detail a mono camera would.

The cheat code, however, is to use a color camera like the ASI294 MC Pro with a duo-narrowband filter like the STC Astro Duo-Narrowband filter. This has the power to build gorgeous deep sky images like the Eagle Nebula example below in a single shot.

The photo above was captured in a Bortle Scale Class 8 light polluted area (my backyard) using the ASI294 MC Pro. It showcases both Ha and OIII gases of this Emission Nebula (Messier 16) for some astonishingly detailed results from the city.

I generally bin my images 2×2, so that just means that my photos are half of that size, in greater resolution. (smaller pixel size). The Bayer pattern of this color sensor is RGGB, which you’ll need to remember when selecting the camera in your image control software, and before stacking.

This camera is well suited for color EAA astronomy (Electronically-Assisted Astronomy), as the ASI294MC Pro includes a 256MB DDR3 memory buffer to help improve data transfer reliability. This is a great feature to consider if you plan on diving into this type of visual astronomy.

You can benefit from the high sensitivity sensor to view more detail in a deep sky object in a “live” looping video feed. Because I am obsessed with collecting images, the only time I experience a glimpse of this feature is when I am framing my target!

All of the Pro model ASI color cameras include the DDR3 Buffer technology which results in faster data transfer speeds and reduces amp glow. Each one of these cameras requires 55mm of back focus between the image sensor and your flattener/reducer.

In the case of the Celestron 8″ RASA F/2, no field flattener is needed as this optical system is very flat to begin with. However, a new backfocus distance is needed between the camera sensor and the top surface of the lens group cell. To achieve the required spacing of 29mm for the RASA, I used a Starizona filter slider drawer to give me some added backfocus.

Making the Upgrade from a DSLR to a CCD-style camera

When I began using color CMOS cameras like the ASI294 MC Pro, I could no longer use the camera control software I did with my DSLR’s (Backyard EOS). Instead, I use an application called APT (Astro Photography Tool), which allows me to control every aspect of the camera from the cooling temperature to gain.

Upgrading from a DSLR to a CCD type astronomy camera like this is a big transition. For me, the hardest part was getting used to controlling the camera entirely with external software.

The change in image file formats (from .RAW to .FITwas also a bit of a hurdle early on. Luckily, DeepSkyStacker is well suited to stack and de-Bayer this image format into a high resolution .TIF file that you can process in Photoshop.

The two-stage TEC (Thermo-electric cooling) is perhaps the biggest difference and advantage a dedicated astronomy camera has over a DSLR. As you may know, noise is a big issue to deal with when taking long exposures at a high ISO. I’ve battled with noise for many years (and continue to do so) when processing my astrophotography images taken with my Canon T3i and 5D Mk II DSLR’s.

A cooled CMOS camera like the ASI294 MC Pro can cool its sensor down to 35 degrees below ambient. This results in images that are virtually free of thermal noise. I should mention that it’s important to understand that this means 35 degrees below the current temperature, so if it’s a hot 30-degree night, the camera will max out at -5 degrees.

Pixel Scale

The pixel size of the ZWO ASI294MC Pro is a great match for many of my astrophotography telescopes. The pixel size of the ASI294 is 4.63µm, which is in the middle of the road for the ASI camera lineup. For comparison, the ASI183MC Pro has a sensor with a 2.4µm pixel size.

So what does this mean for your astrophotography images?

In the amateur astrophotography community, a general rule of thumb is to use a pixel scale that is between 1.0 to 2.0 to be “well sampled”. This is simply a rough guideline and should not be taken too literally. The math for calculating the pixel scale of a particular camera and telescope combination is:

pixel size (4.63) / focal length (550) x 206 = 1.73

When using the ZWO ASI294MC Pro with the Celestron 8″ RASA F/2, I have a pixel scale of 2.38 which some consider to be “under-sampled”. Theoretically, under sampling can lead to blocky or pixelated stars in your image, although in reality I have never known this to be a noticeable problem (in any of my telescopes).

Compare this to the Sky-Watcher Esprit 100, which provides me with a pixel scale of 1.73. The bottom line is, it’s worth calculating the pixel scale of your camera and telescope combo before making any big decisions. In my experience, the ZWO ASI294 is an extremely versatile choice for many telescope focal lengths.

Connections and Software

The camera is connected to my computer via a USB 3.0 cable. For the cooling feature, it also requires an external 12V power supply that does not come included with the camera. If you’re anything like me, you have accumulated a number of 12V adapter cables over the years.

To keep things organized and convenient, I now connect the power port on the ASI294MC Pro to the outlets on my Pegasus Astro Pocket Power Box. This means that the camera and telescope don’t have another power cable running to an outlet. It all rides atop the iOptron CEM60 equatorial mount.

The camera is controlled using APT, which required the appropriate drivers from the ZWO ASI website. Installing the driver is painless, and then the “ASI camera” selection will appear from the drop-down menu the next time you connect the camera to APT.

The cooling function is set using the “Cooling Aid” within Astro Photography Tool. It can take a few minutes to get the camera sensor to the temperature you want it. It’s best to get a head start on this process so you’re not waiting around when it’s time to shoot.

A One-Shot-Color Camera – Impressive Specs

I love how sensitive the SONY IMX294CJK sensor is on this camera. The dynamic range of this camera sensor is listed at 13 stops. This is even more than the legendary AS1600 camera from ZWO. This characteristic is thanks to the built-in 14bit ADC (analog-to-digital converter) unit on the 294MC Pro.

ZWO ASI294MC Pro Camera Specs:

Sensor: 4/3″ SONY IMX294 CMOS

Diagonal: 23.2mm

Resolution: 10.7 Mega Pixels (4144 X 2822)

Pixel Size: 4.63µm

Bayer Pattern: RGGB

ADC:14bit

DDRIII Buffer: 256MB

Back Focus Distance: 6.5mm

Cooling: Regulated Two Stage TEC

If you’re wondering what the difference is between the MC-Cool and MC-Pro cameras from ASI are, it’s the DDR3 memory buffer. For non-tech-heads (like myself) this basically means that the camera can transfer data faster and more efficiently. It also reduces amp glow because this artifact is primarily caused by slow transfer speeds.

Here is what the amp glow looks like on a single image captured with the ASI294MC Pro. The amp glow is completely removed after stacking the images with dark frames in DeepSkyStacker.

Recommended settings for the ASI294 MC Pro

I find that the best camera settings to use with this camera are to set the gain at “unity gain” and an exposure length of 3 to 5 minutes. This, of course, depends on the deep sky target you are shooting, and the filters being used with the camera.

For example, using a narrowband filter such as a 12nm Ha, I would choose an exposure length of at least 5 minutes. I even shot some images that were as long as 10 minutes with this camera. The photo below shows the Rosette Nebula using a stack of 20 x 10 minutes exposures using the ASI294MC Pro and an Astronomik 12nm Ha filter.

Because the sensor is so sensitive, I can often find my deep sky target in a 2-3 second exposure in live loop mode. This is usually with a strong narrowband filter in front, which is quite impressive. This makes framing the target much easier because you’re able to see the shape and orientation of the DSO (almost) in real time as you adjust the telescope.

Taking flat frames with the ASI294MC Pro

I use 3 layers of white t-shirts when capturing flat frames with the ASI29MC Pro. I point the telescope towards the morning dawn sky with the t-shirts covering the telescope objective.

When the white t-shirt method isn;t cutting it, a flat field panel like the Artesky Flat Field Generator works exceptionally well.

Taking flat frames with the ASI294MC Pro using a flat field panel (Artesky Flat Field Generator).

I use the CCD Flats Aid tool in Astro Photography Tool to find the correct exposure to hit my target ADU (25,000). In my experience the images are usually around an exposure of 0.03381 when using a gain setting of 120 (unity gain). This creates a flat field image with an ADU of approximately 25000.

I have heard that others have found success by using longer flat frame exposures, which can be accomplished by adding more layers of white t-shirts or with an adjustable flat panel.

Final Thoughts

If you compare the ASI294MC Pro vs. the ASI071MC Pro, you’ll find that the price is significantly more affordable for the 294. I’ve used both of these cameras (The ASI071 camera was the older non-pro “Cool” version), and the image results are remarkably comparable.

The biggest difference between the two cameras is, of course, the sensor itself. The sensor in the AS071 is a 16MP APS-C sized chip, while the ASI294 is a four-thirds 10.7 MP sensor. This changes the pixel scale of your images and thus the apparent size of the objects you’ll capture through your telescope.

For APO refractors in the 700-1000mm range, the pixel scale of the ASI294 MC Pro was the absolute perfect size for some of my favorite deep sky targets like the Eagle Nebula and Pelican Nebula. I used a Starfield 0.8X reducer/flattener with this camera and the various refractor telescopes I used when imaging deep sky objects.

If you’re looking to upgrade your DSLR or current color astronomy camera to the realm of “cooled” CMOS sensors – my results with the ASI294 MC Pro should help you make a more informed decision. I highly recommend the ASI294 MC Pro camera if you are in the market for a color astrophotography camera with some serious power and versatility.

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